This invention pertains to a type of conductor wires for making electric connection of a semiconductor chip to external conductors. In particular, this invention provides an excellent type of conductor wires that can reduce the thickness of the package and can avoid problems of short-circuits among the wires.
Wire bonding is the most common method for connecting a semiconductor chip to external conductors, such as a pattern or lead frame on an insulating substrate. In the wire bonding method, the semiconductor chip is connected to the external conductors by fine wires of gold (Au) or aluminum (Al) fed from a tool known as a capillary tool. In the manufacturing process, the wires fed from the capillary tool have one end bonded to the electrode pads of a semiconductor chip, followed by looping, that is, forming a loop, and then have the other end bonded to the external conductors.
The aforementioned wire looping plays an important role in absorbing the influence of contraction of the wires under pressure and heat during the molding operation. On the other hand, however, the amount of rise of the wire loops from the surface of the semiconductor chip directly affects the thickness of the semiconductor device. It is necessary to have sufficiently thick packaging material on the surface of the semiconductor chip to completely cover and shield the aforementioned wires. On the other hand, with the miniaturization trend of electronic and communications equipment, there is a requirement for even smaller and thinner semiconductor devices. Consequently, it is important to further reduce the thickness of the packaging material on tile semiconductor chip.
On the other hand, with progress in realizing higher speeds and more functions for semiconductor devices, the number of connecting terminals of semiconductor devices is on the rise. An increase in the number of the connecting terminals means an increase in the number of the wires inside the device. As a result, along with the aforementioned demand for smaller device sizes, the danger of short-circuits between adjacent wires becomes higher. That is, as the distance between adjacent wires becomes smaller, spread of the wire configuration during manufacturing and deformation of the wires during injection molding lead to short-circuits of the wires. When electrode pads (2) are set in a zigzag pattern on semiconductor chip (1), as shown in FIG. 6, it is possible to increase the number of connecting terminals per unit area. As the distance between wires W is further reduced, the aforementioned problem becomes exacerbated.
As a method for solving the aforementioned problems, a bending point usually called the xe2x80x9cbendxe2x80x9d (point P in the figure) is formed midway along wire W, as shown in FIG. 7, so as to increase the resistance to deformation. However, even with such a bending point, it is still impossible to eliminate deformation of the wires, and there is still a danger of short-circuits, depending on the configuration of the wires.
As another method to reduce the danger of wire short-circuits, as shown in FIG. 8, the heights of adjacent wire loops are changed alternately in bonding. Even when adjacent wires move near each other in the plane due to the movement of wires during manufacturing, it is still possible to ensure a sufficient gap between the wires in the height direction, and it is thus possible to minimize the danger of short-circuits. However, in order to ensure a sufficient gap in the height direction, the thickness of the packaging material on the semiconductor chip has to be increased. This is a disadvantage.
The purpose of this invention is to provide a type of conductor wires appropriate for realizing a thin semiconductor device.
Another purpose of this invention is to provide a type of conductor wires that can minimize the problem of short-circuiting between wires while the thickness of the semiconductor device is reduced.
This invention pertains to a type of conductor wires for electrically connecting the semiconductor chip to external conductors. Each of the conductor wires in this invention has a first end portion bonded to the electrode pad of the semiconductor chip, a second end portion bonded to the external conductor, and a bending point which is positioned between the aforementioned first and second end portions and is bent almost in the direction opposite to the direction that the conductor wire rises at the aforementioned first end portion. The aforementioned bending point is usually called the xe2x80x9cbend.xe2x80x9d It refers to the site on the wire intentionally bent during manufacturing. As the bending point is bent almost in the direction opposite to the rising direction of the conductor wire, it is possible to reduce the amount of rise of the conductor wire from the principal surface of the semiconductor chip, so that the semiconductor device can be made even thinner.
According to this invention, in order to reduce the amount of rise of the conductor wire as much as possible, it is preferred that the aforementioned bending point be positioned on the side opposite to the rising side of the conductor wire with respect to the position of a straight line connecting the aforementioned first end portion and the aforementioned second end portion, and that the bending point position be shifted toward the aforementioned first end portion.
Also, in order to further increase the resistance of the conductor wires to deformation, plural said bending points may be formed on each conductor wire.
This invention also provides a type of semiconductor device having the aforementioned conductor wires. The semiconductor device of this invention has plural first conductor wires and plural second conductor wires set close among the aforementioned first conductor wires. Each said first conductor wire has a bending point bent in the rising direction of the conductor wire. Each said second conductor wire has a bending point bent in the direction almost opposite to the rising direction. In this way, a sufficient gap is formed between the conductor wires having bending points in different directions, and the possibility of short-circuits is reduced.